Weekly Hydro-meteorological Report, 19, April 2018

Highlights:

•   The NCEP weekly rainfall forecast predicts total rainfall between 55-65 mm in Galle and Kalutara districts during 19th -25th Apr.
•   Between 11-17 Apr: up to 90 mm of rainfall was recorded in Gampaha and Kegalla districts on April 12th.
•   From 8-14 Apr: minimum temperature of 15 ^OC was recorded from Nuwara Eliya district while Puttalam and Kurunegala districts recorded a maximum temperature between  30-35 ^OC.
•   From 10-16 Apr: up to 20 km/h, easterly winds were experienced by the entire island.
•   0.5 ^OC above average sea surface temperature was observed in the northern seas of Sri Lanka.

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Summary

Monitoring

Weekly Monitoring: On April 11th, Kalutara, Galle and Matara districts received up to 60 mm of rainfall; Ratnapura, Hambantota and Batticaloa districts up to 30 mm; Trincomalee, Polonnaruwa, Ampara, Monaragala, Nuwara Eliya, Kegalla, Kurunegala, Puttalam, Gampaha and Colombo districts up to 20 mm; and rest of the country up to 10 mm. On the 12th, Gampaha and Kegalla districts received up to 90 mm of rainfall; Colombo, Kalutara, Galle and Matara districts up to 50 mm; Puttalam, Anuradhapura, Kurunegala, Badulla, Ratnapura Nuwara Eliya and Hambantota districts up to 30 mm; Mullaitivu, Vavuniya, Polonnaruwa, Matale, Trincomalee, Batticaloa, Kandy and Ampara districts up to 20 mm; and rest of the island up to 10 mm. On the 13th, Jaffna, Mannar, Anuradhapura, Puttalam and Kurunegala districts received up to 30 mm of rainfall; Kilinochchi, Mullaitivu, Vavuniya and Trincomalee districts up to 20 mm; and most parts of the island up to 10 mm. On the 14th, Puttalam, Kandy and Nuwara Eliya district received up to 50 mm of rainfall; Anuradhapura, Kurunegala, Ratnapura, Matale and Badulla districts up to 30 mm; Kegalla, Gampaha, Kalutara, Galle and Matara districts up to 20 mm; and rest of the country up to 10 mm. On the 15th, Anuradhapura district received up to 50 mm; Kurunegala district up to 30 mm; Kilinochchi district up to 20 mm; and rest of the northern and central regions of the island up to 10 mm. On the 16th, Kurunegala district received up to 50 mm of rainfall; Gampaha district up to 30 mm; and Puttalam, Kegalla, Colombo, Kalutara, Galle, Matara, Hambantota, Ratnapura, Badulla and Monaragala districts up to 20 mm. On the 17th, western coastal regions of the island received up to 10 mm of rainfall.

Total Rainfall for past week :  The RFE 2.0 tool shows total rainfall of 100-150 mm in Gampaha and Kurunegala districts; up to 75-100 mm in Puttalam, Anuradhapura, Colombo, Kegalla, Kalutara, Galle, Matara and Hambantota districts; up to 50-75 mm in Matale, Kandy and Nuwara Eliya districts; and up to 25-50 mm in rest of the island. It also shows above average rainfall up to 50-100 mm in Galle district; and up to 25-50 mm in Jaffna, Puttalam, Gampaha, Matara and Hambantota districts. Below average rainfall up to 50-100 mm is shown for Kurunegala district; and up to 25-50 mm in Anuradhapura, Matale, Kandy and Monaragala districts.

Monthly Monitoring: During March - below average rainfall conditions were mainly experienced by northern and central regions of the island. Vavuniya, Mullaitivu, Mannar, Trincomalee, Anuradhapura, Polonnaruwa, Kurunegala, Puttalam, Kandy, Nuwara Eliya, Ratnapura, Matara and Kegalla and western regions of Matale district received up to 120 mm below average rainfall. Above average rainfall up to 90 mm was received by Jaffna, Kilinochchi, Colombo, Galle, Hambantota, Badulla, Monaragala, Ampara and Trincomalee districts. The CPC Unified Precipitation Analysis tool shows ~300 mm of total rainfall in Kalutara, Galle and Ratnapura districts; up to 200 mm Kurunegala, Matale, Kegalla, Nuwara Eliya, Badulla and Monaragala; up to 100 mm Puttalam, Anuradhapura, Polonnaruwa, Trincomalee, Ampara and Hambantota districts;and up to ~75 mm in Jaffna, Kilinochchi and Vavuniya districts. 

Predictions

14-day prediction:
NOAA NCEP Models:

From 19th -25th Apr: Total rainfall between 55-65 mm in Kalutara and Galle districts; between 45-55 mm in Ratnapura, Matara and Hambantota districts; between 35-45 mm in Gampaha, Colombo, Kegalle, Nuwara Eliya and Monaragala districts; between 25-35 mm in Puttalam, Kurunegala, Kandy and Badulla districts; between 15-25 mm in Ampara district; between 5-15 mm in Anuradhapura, Matale, Polonnaruwa and Batticaloa districts; Up to 5 mm total rainfall rest of the island.

From 26th Apr – 02nd May: Total rainfall between 95-105 mm in Galle district; between 85-95 mm in Kalutara and Matara districts; between 75-85 mm in Ratnapura and Hambantota districts; between 65-75 mm in Colombo, Kegalle, Nuwara Eliya, Monaragala and Hambantota districts; between 55-65 mm in Gampaha, Kandy and Hambantota districts; between 45-55 mm in Ampara district; Up to 35 mm total rainfall rest of the island.

IMD WRF Model Forecast: 

21st Apr: Up to 7.6 mm of rainfall in Mullaitivu, Vavuniya, Mannar, Anuradhapura, Puttalam, Polonnaruwa, Trincomalee, Galle and Hambantota districts; Up to 2.5 mm in Jaffna, Kilinochchi, Kurunegala, Matale, Batticaloa, Ampara, Badulla, Monaragala, Ratnapura, Matara, Kalutara, Colombo and Gampaha districts.

22nd Apr: Up to 7.6 mm of rainfall Mullaitivu, Mannar, Vavuniya, Anuradhapura, Puttalam, Polonnaruwa, Gampaha, Colombo, Kalutara, Galle, Matara, Hambantota and Ratnapura districts; Up to 2.5 mm in Jaffna, Kilinochchi, Trincomalee, Matale, Batticaloa, Ampara, Badulla and Monaragala districts.

IRI Weekly forecast:
From 18th – 23rd Apr: Total rainfall between 25-50 mm in Matale, Kandy, Kegalle, Ratnapura, Nuwara Eliya, Badulla, Monaragala, Ampara and Hambantota districts; Up to 25 mm total rainfall rest of the island.

Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : April 12, 2018

In early April 2018, the east-central tropical Pacific still reflected weak La Niña conditions. Most of the key atmospheric variables also show patterns suggestive of La Niña, but also only weakly, and the east Pacific subsurface water temperature has become above average. The official CPC/IRI outlook calls for a transition from La Niña to neutral conditions during the March-May season. The latest forecasts of statistical and dynamical models support this scenario.

INDIAN OCEAN STATE :   0.5 ^OC above average sea surface temperature was observed in the northern seas of Sri Lanka.

MJO STATE :  MJO shall enhance the rainfall in Sri Lanka in the next 10 days and shall not have a impact in the following 5 days.